Growing Carnivorous Plants in Arizona: Notes from a Chandler Greenhouse

Canyon Exotics grows in Chandler, in the East Valley of the Phoenix metro. People picture carnivorous plants in a bog and assume the desert is the wrong place for them. Arizona is a hard place for some carnivorous plants and a good one for others, and the difference comes down to water, heat and dry air. This is what we tell customers who live here.

What works against you

Phoenix summer highs run above 105°F for weeks at a stretch between June and September. Afternoon humidity in May and June regularly drops into the teens or lower. And the tap water is hard: Chandler's municipal water carries several hundred parts per million of dissolved minerals, well beyond what any carnivorous plant tolerates. A plant that would shrug off a windowsill in Ohio can decline in a week on a Phoenix patio.

None of that rules them out. It means choosing plants that cope with dry air, keeping them indoors through the worst of the summer, and never letting tap water near them.

Water first

Carnivorous plants evolved in mineral-poor soil and get their nutrients from insects. Minerals in the water build up in the root zone and burn the roots. In Arizona this is the most common way a new plant dies.

Use distilled water, reverse-osmosis water or collected rainwater. A gallon of distilled water costs about a dollar at the grocery store, and a small butterwort uses very little. If you have an RO tap for drinking water, that works. Rain collected during the monsoon is fine as long as it did not run off a roof or gutter treated with anything. Do not use softened water. A softener swaps calcium and magnesium for sodium, which is worse for the plant.

Light: bright, but not a west window in July

Mexican butterworts and Cape sundews want bright light, and Arizona has more of it than almost anywhere. The problem is intensity. Direct afternoon sun through a west-facing window in summer scorches leaves and heats the pot. An east-facing window gives strong morning light and shade by midday, which is close to ideal. A north window is usually too dim to bring out the pink in a butterwort, although the plant will live.

Under lights, a small LED grow light 6 to 12 inches above the plant for 12 to 14 hours a day gives the same result every day of the year and takes the window out of the equation. Our own plants are grown indoors under lights year-round for the same reason.

Humidity: less of a problem than you expect

Many Mexican Pinguicula come from limestone slopes that go dry for months, and they handle the 20 to 30 percent humidity of an air-conditioned Arizona house without a terrarium or a humidifier. Dew may thin out a little in the driest weeks, and that is all.

Cape sundews want more moisture, but they get it from the pot, not the air. Stand the pot in a shallow tray of distilled water through the growing season and the plant will be fine in dry air. Do not use the tray on a butterwort; they rot in standing water.

One local note: air conditioning dries a room and an evaporative cooler humidifies it. Plants near a swamp cooler vent are often the happiest in the house in June, and the fussiest in August once the cooler is switched off for the monsoon.

Summer: keep them inside

From late May until the monsoon breaks, grow indoors. A covered patio still reaches 100°F or more in the afternoon, and a small pot can heat past what the roots survive. Indoors under air conditioning, a butterwort on an east windowsill or under a light grows straight through the summer and often blooms.

The monsoon, which usually gets going in early July and fades in September, raises the humidity and brings cloud. That helps. Still, humid air in a closed room invites fungus, so a ceiling fan or an open interior door is worth having.

Winter: watch the frost nights

Winter is the easy season. Mexican butterworts do not need a cold dormancy, and most shift to a compact winter rosette on their own as days shorten and nights cool. Water them much less in that phase. Our note on the winter rosette covers it.

The one hazard is frost. The East Valley gets a handful of nights below 32°F most winters, usually in December and January. Mexican Pinguicula and Cape sundews are frost tender. If a plant spends the cool season on a patio, bring it in whenever the forecast drops below 40°F. That same threshold is why we hold shipments in cold weather.

Which plants suit Arizona

For a first plant in the desert, a Mexican butterwort is the safest choice we know: it tolerates dry air, grows well under a light, and catches fungus gnats all year. 'Johanna' and 'Pirouette' are the two we recommend most often. A Cape sundew is the next step if you will commit to the water tray. Temperate plants such as Venus flytraps and North American pitcher plants can be grown outdoors here in a bog tub, but they need far more water, a real winter dormancy and careful summer shade, and we do not grow them.

Common questions

Can I grow a butterwort outdoors in Phoenix?

In spring and fall, yes, on a shaded patio out of the afternoon sun. From late May to mid-September bring it indoors; the heat is more than a small pot can buffer. Bring it in again on any night forecast below 40°F.

Is Phoenix tap water safe for carnivorous plants?

No. Valley tap water carries far too much dissolved mineral. Stick to distilled, reverse-osmosis or rainwater. Tap water damage is slow: the plant stops pushing new leaves, the old ones brown, and it fades over a few weeks.

Do I need a humidifier or terrarium?

Not for a Mexican butterwort. Ordinary air-conditioned household air is fine. A Cape sundew gets its moisture from a water tray rather than from the air.

Does the monsoon help or hurt?

It helps. Higher humidity and cloud cover take the edge off summer. The only thing to watch is still, humid air indoors, which encourages fungus. A little air movement fixes it.

Where to go next

The full routine for light, water, potting and the winter rest is in the care guide. If fungus gnats brought you here, read using Pinguicula to control fungus gnats. Sundew growers should start with the Cape sundew care guide. Everything we grow, all of it raised here in Chandler, is in the shop.